1. Field of the Invention
The invention relates to a submount for electronic components according to the preamble to claim 1. In addition, the invention relates to an assembly with at least one such component and to a process for producing such an assembly according to one of the associated claims.
2. Description of the Related Art
Electronic components, in particular opto-electronic components, are conventionally mounted onto a submount which, for example, consists of silicon or of ceramic material. Contact areas for the electrical contacting of the components are located on the surface of the submount. Contacting is conventionally effected by so-called bonding, a process wherein the contacts on the upper side of the components are connected to one another to the contact areas of the submount via fine gold wires. The contacts located on the underside of the components are connected to the contact areas in accordance with the so-called flip-chip process. For correct positioning of the components, base areas are conventionally provided which frequently consist of glass material that is also used for producing optical waveguides. This technology is frequently employed in the domain of optical message transmission, in which laser-generated light is modulated and transmitted. The assemblies consisting of one or even several components have to be very powerful, this being required especially in the domain of optical telecommunications where very short switching-times of less than 200 picoseconds and correspondingly high data-transfer rates of up to 10 Gbit/s are to be attained. The components that are used are, for example, opto-electronic switching circuits which are constructed as optical transmitters or amplifiers. In the case where several components are arranged on a submount, so-called crosstalk may arise between components that are directly adjacent to one another. This interference effect clearly reduces the signal/interference ratio of the message signals and hence the performance of the assembly.
An assembly with a submount and with opto-electronic components arranged thereon is known from DE-A-195 22 591. The subassemblies described therein include, inter alia, an optical coupler, an emitting light source connected to said optical coupler, and light-signal detectors. In order to reduce the electrical crosstalk arising between the light source and the light detectors, the light source, on the one hand, and the light detectors, on the other hand, are arranged in this patent on opposite sides of the coupler. Hence the mutually interfering components are accordingly arranged far away from one another, in order to achieve a spatial separation that is as great as possible. But this measure cannot always be implemented, in particular not in the case of highly integrated assemblies. In addition, this measure conflicts with the desire to be able to configure the placement of the components on the submount as freely as possible.
The object of the invention is to create a submount for electronic components, with which the aforementioned problems do not arise. In addition, an assembly with such a submount and a process for producing such an assembly are to be proposed.
The object is achieved by means of a submount having the features according to claim 1 and also by means of an assembly and a process having the features according to one of the associated claims.
Accordingly, a submount for electronic components is proposed that has a surface on which a first contact area and a second, opposite-pole contact area for the electrical contacting of one of the electronic components are applied and that has, at least beneath the point at which the first contact area is located, a depression which is provided with a metal film and filled with a dielectric, the metal film being electrically connected to the second contact area.
Correspondingly, the assembly according to the invention has at least one electrical component and a submount with a surface on which a first contact area and a second contact area for the electrical contacting of the electronic component are applied. And the assembly is characterised in that the submount has, at least beneath the point at which the first contact area is located, a depression which is provided with a metal film and filled with a dielectric, and in that the metal film is electrically connected to the second contact area. With a view to producing the assembly, in accordance with the invention a depression is accordingly introduced into the submount, at least beneath the point at which the first contact area is located, the depression being provided with a metal film and filled with a dielectric, and the metal film being electrically connected to the second contact area.
The invention proceeds from the perception that in the case of a traditional submount the interfering crosstalk is substantially brought about by field lines arising that extend between the opposite-pole contact areas, whereby they penetrate for the most part into the material of the submount and are propagated from the region of one component to the regions of the adjacent components and beyond. By virtue of the measures according to the invention, however, the field lines are concentrated in the depression which is filled up with the dielectric, whereby the metal film which is applied there shields the material of the submount against penetration of the field lines. Accordingly a region defined by the dimensions of the depression between the first contact area and the metallic surface (opposite pole) connected to the second contact area is created, in which the greater part of the field lines is captured. The creation of a depression has the advantage that the overall height of the new arrangement is preserved in comparison with a traditional arrangement. In addition, the coating of the depression with metal and the subsequent filling with a dielectric can be carried out very precisely with a thin-film process known as such. The invention, which is simple to realize, as well as the advantages resulting from the invention, will be described in detail later.
Particular advantages of the invention are evident from the dependent claims:
It is accordingly particularly advantageous if the depression is filled with a polymer up to a height that terminates with the surface of the submount. For the polymer can already be processed very easily when heated to 400xc2x0 C., for example, i.e. at a temperature far below the melting-temperature of glass or metal, and can be introduced into the depression. The filling-height can also be adapted exactly to the level of the surface of the submount, as a result of which the original overall height of the total arrangement is preserved.
It is advantageous if the metal film and the dielectric are established by thin-film technology. Hence a very precise geometry of the arrangement can be conformed to.
The submount preferably consists of silicon, and the component is preferably an opto-electronic component. In addition, it is advantageous if the first contact area together with at least two base areas connect the component to the submount in accordance with the flip-chip method. By this means, a very rapid and exactly fitting positioning and also contacting of the component is obtained. In this context it is a particular advantage if the base areas consist of a glass material.